I'm a developer.
When I change my window position to coordinate {0,0} I suppose it must goes to upper-left desktop corner (TaskBar is located at the bottom).
But that does not happen anymore (Win10 build 9xxx and 10041).
In other words, calling SetWindowPos(hWnd, NULL, 0,0,0,0, SWP_NOSIZE) leaves a gap at the left.
And more, if I get the dimension of desktop work area and set appropriate window height - gap at the bottom appears too.
That is a breaking change of coordinate system. It has worked properly before, up to Windows 8.1.